Higher abundance of dietary sulfur-reducing microbes was associated with increased risk of colorectal cancer

1. In this study, long-term high sulfur microbial diet was associated with increased risk of colorectal cancer.

2. Body weight and family history of colorectal cancer did not modify association between high sulfur microbial diet and colorectal cancer risk.

Evidence Rating Level: 2 (Good)

A diet high in low-calorie beverages and animal protein and fat has been thought to potentially increase intestinal sulfide production by gut microbiota and consequently increase the risk of colorectal cancer (CRC). However, the role of gut microbes that reduce dietary sulfur to potentially carcinogenic hydrogen sulfide in modulating risk of CRC has not been extensively tested.

This study pooled data from three prospective cohort studies of 214,797 adult male (40-74 years old) and female (25 to 55 years old) United States (US) health professionals, in which dietary intake was assessed using semi-quantitative food frequency questionnaire (FFQ) starting from 1986, 1984, and 1991. Participants who had a prior diagnosis of CRC, inflammatory bowel disease, or other cancers were excluded. Stool samples were collected from select group of participants (developmental cohort) from 2012-2014 and sequenced to identity gut microbiota composition. The relative abundance of 43 previously identified sulfur-metabolizing bacteria was determined in the 519-participant developmental cohort. The primary outcome was incidence of CRC, which was determined based on self-reported diagnosis of CRC in biennial questionnaires, medical records, tumor registries, and death certifications.

In this study, greater adherence to sulfur microbial diet was associated with increased risk of CRC (hazard ratio 1.27) and particularly, distal CRC (hazard ratio of 1.25). Overall, long-term adherence to sulfur microbial diet was associated with higher abundance of sulfur-metabolizing gut bacteria and increased risk of CRC. However, this study was limited in its homogenous study population of US health professionals which minimized sociodemographic confounding, warranting further study. Nonetheless, this study was significant in suggesting that adherence to a sulfur microbial diet (including red meats, low intake of fruits, whole grains, vegetables) is associated with increased risk of CRC.

Click to read the study in JAMA Network Open

Image: PD

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